This project coupled two existing models to quickly generate flow and flood-inundation estimates at high resolutions over large spatial extents for use in emergency response situations. Input data are gridded runoff values from a climate model, which are used by the Routing Application for Parallel computatIon of Discharge (RAPID) model to simulate flow rates within a vector river network. Peak flows in each river reach were then supplied to the AutoRoute model, which produces raster flood inundation maps. The coupled tool (AutoRAPID) was tested for the June 2008 floods in the Midwest and the April-June 2011 floods in the Mississippi Delta. RAPID was implemented from 2005 to 2014 for the entire Mississippi River Basin (1.2 million river reaches) in approximately 45 min. Discretizing a 230,000-km2 area in the Midwest and a 109,500-km2 area in the Mississippi Delta into thirty-nine 1° by 1° tiles, AutoRoute simulated a high-resolution (~10 m) flood inundation map in 20 min for each tile. The hydrographs simulated by RAPID were found to perform better in reaches without influences from unrepresented dams and without backwater effects. Flood inundation maps using the RAPID peak flows varied in accuracy with F-statistic values between 38.1 and 90.9%. Better performance was observed in regions with more accurate peak flows from RAPID and moderate to high topographic relief.
